The invention relates to offshore oil production and in particular to a modular apparatus for tensioning production risers to a floating platform.
In the production of oil to a tensioned leg floating platform a conductor or riser has its lower end secured to a connection at the seabed. The upper end of the riser is terminated at the platform. The marine riser will collapse if not partially or completely supported at the upper end. It, therefore, is conventionally supported by a tensioned forced applied at the upper end of the riser.
Because of the relative motion between the platform and the seabed caused by wave and tide actions, some device is required to maintain the tension while permitting the relative motion.
This has conventionally been accomplished on other types of floating vessels with hydraulic-pneumatic tensioning devices mounted on the vessel structure and connected to the riser with a plurality of wire ropes. The conventional method requires considerable deck space and makes changing of tensioners between various locations difficult and impracticable for floating platform use. The wire rope requires constant maintenance, is subject to wear with potential failure, and the use of the rope delays the response time of the tensioning system.